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Onychomycosis (cont.)

What Causes a Fungal Nail Infection?

Fungal nail infection is caused by three main classes of organisms: fungi that infect hair, skin, and nails and feed on nail tissue (dermatophytes), yeasts, and non-dermatophyte molds. All three classes cause the very similar early and chronic symptoms or appearances, so the visual appearance of the infection may not reveal which class is responsible for the infection. Dermatophytes (including Epidermophyton, Microsporum, and Trichophyton species) are, by far, the most common causes of fungal nail infection worldwide. Yeasts cause 8% of infections, and non-dermatophyte molds cause 2% of fungal nail infections.

  • The dermatophyte Trichophyton rubrum is the most common fungus causing distal lateral subungual onychomycosis (DLSO) and proximal subungual onychomycosis (PSO).
  • The dermatophyte Trichophyton mentagrophytes commonly causes white superficial onychomycosis (WSO), and more rarely, WSO can be caused by species of non-dermatophyte molds.
  • The yeast Candida albicans is the most common cause of chronic mucocutaneous candidiasis (disease of mucous membrane and regular skin) of the nail.

What Are Fungal Nail Infection Risk Factors?

Risk factors for fungal nail infection include family history, advancing age, poor health, trauma, living in a warm climate, participation in fitness activities, immunosuppression (can occur from HIV or certain drugs), bathing in communal showers (such as at a gym), and wearing shoes that cover the toes completely and don't let in any airflow.

Fungal nail infections, especially toenail infections, can be contagious person to person from direct and indirect contact with an infected person or their clothing, such as wearing an infected person's shoes or socks. The incubation period for a fungal nail infection is about three to six days.

Medically Reviewed by a Doctor on 2/2/2016

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Read What Your Physician is Reading on Medscape

Onychomycosis »

Onychomycosis (OM) refers to a fungal infection that affects the toenails or the fingernails.

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